help.

So me and my SO have a 2 month old son. and he has always had this friend "t" (what we will call her" and he has always seemed to have some sort of attachment to her. like he will text her about her day or ask how schools going. he talked to her the whole time i was in labor and even invited her to meet the baby when he was born without my permission. well she recently got engaged to her long time boyfriend and he acts so weird about it when we talk about her engagement. like he avoids the conversation when someone brings it up. and her, her brothers, and fiancé came over for drinks a couple nights ago and i would occasionally look at him just to find him staring at her and as soon as he caught me looking at her he would get up and walk away. Another weird thing that night was on the radio that "marry me" song by thomas rhett came on and every time it came on (2 or more times that night & if you don't know the song is about him being in love with a girl who's getting married to someone who isn't him and he's heartbroken about it) he would walk outside to smoke hanging his head. idk what to think. trying not to think the worst but i feel like he's in love with her.